Usually, in a vehicle or the like, a plurality of electric devices are electrically connected to one another by a plurality of electric wires (referred to frequently and simply as wires). The wires are bundled, by an insulation locking band, tape or the like, into a single bundle as so-called wire harness which is extendedly arranged at predetermined locations of the automobile or the like. In some eases, the wires are protected by a wire protecting member such as a grommet, and are arranged at a predetermined part. In other cases, the wires are arranged at a predetermined part of the vehicle or the like, while not bundled into one line and/or not protected by the wire protecting members.
The vehicle is always placed in such an environment that it is always vibrated due to engine drive and the like. In particular, the electric wires distributed inside the engine room directly receiving the engine vibrations, are repeatedly bent and deformed, and finally disconnect due to the vibrations. Experimental results of such are reported. In this respect, it is of particular importance to accurately predict the bending life spans of the electric wires and the wire protecting members.
Generally, the prediction of the bending life spans of the electric wires and the wire protecting members is carried out by repeating design, trial manufacturing, and endurance test. For example, in such an endurance test, wires distributed along an envisioned wiring path are placed on a vibration base plate. The vibration base plate is vibrated at a predetermined frequency and a predetermined amplitude by the vibrator, and a bending life span of the wire when it is vibrated at a specific number of vibrations is predicted.
The literature cited in the present specification are: Non-patent document 1
“Matrix Infinite Element Method” by B. Nasu, published by Brain Library Publishing Corp, Aug. 10, 1978, pp 7 to 15 Non-patent document 2
“Mode Analysis and Dynamic Design” by Kimihiko Yasuda, published by Corona Corp, Nov. 10, 1993, pp 54 to 56
On the other hand, a development period of the vehicle tends to be shorter, and further there is a demand of enhancing a bending life prediction accuracy. In this circumstance, the related bending life span predicting method in which the endurance test is repeated cannot satisfactorily reduce the development period, and cannot sufficiently meet the demand of enhancing the prediction accuracy.